On 05-06-2023 15:38, Krzysztof Kozlowski wrote:
On 05/06/2023 15:34, Mike Looijmans wrote:
Add bindings for a fixed-rate clock that retrieves its rate from an
NVMEM provider. This allows to store clock settings in EEPROM or EFUSE
or similar device.
Component shortages lead to boards being shipped with different clock
crystals, based on what was available at the time. The clock frequency
was written to EEPROM at production time. Systems can adapt to a wide
range of input frequencies using the clock framework, but this required
us to patch the devicetree at runtime or use some custom driver. This
provides a more generic solution.
Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
---
Changes in v3:
Modify fixed-clock instead of introducing nvmem-clock
Changes in v2:
Changed "fixed-clock" into "nvmem-clock" in dts example
Add minItems:1 to nvmem-cell-names
.../bindings/clock/fixed-clock.yaml | 25 ++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/clock/fixed-clock.yaml b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
index b0a4fb8256e2..23e4df96d3b0 100644
--- a/Documentation/devicetree/bindings/clock/fixed-clock.yaml
+++ b/Documentation/devicetree/bindings/clock/fixed-clock.yaml
@@ -12,7 +12,9 @@ maintainers:
properties:
compatible:
- const: fixed-clock
+ enum:
+ - fixed-clock
+ - fixed-clock-nvmem
Do you even need new compatible? Isn't this the same clock from the
hardware point of view?
I need a new compatible because a "fixed-clock" only loads at init time.
It registers using CLK_OF_DECLARE, which requires the clock to register
early. NVMEM providers are typical devices like I2C EEPROMs that won't
be available at that point, hence I needed to create a clock that
registers as a regular clock driver and can handle deferral and similar.
"#clock-cells":
const: 0
@@ -33,6 +35,27 @@ required:
additionalProperties: false
Put it under allOf. Entire block should be before additionalProperties
(just like in example-schema).
+if:
+ properties:
+ compatible:
+ contains:
+ const: fixed-clock-nvmem
+
+then:
+ properties:
+ nvmem-cells:
+ maxItems: 2
Anyway, I don't think you tested it. Provide a DTS user of this. I don't
think it works and such user would point to mistakes.
Properties should be defined in top-level properties:, not in
allOf:if:then. In allOf:if:then you only narrow them.
Ah, got it. Added an example dts block to the document, this revealed
the issues, indeed didn't test the bindings.
Fixed it into an "allOf" to properly narrow the properties.
I'll test and post a v4 in a jiffie.
+ description:
+ Reads clock-frequency and/or clock-accuracy from an NVMEM provider in
+ binary native integer format. The size of the NVMEM cell can be 1, 2, 4
+ or 8 bytes. If the contents of the nvmem are all zeroes or all 0xff, the
+ value reverts to the one given in the property.
+
Best regards,
Krzysztof
--
Mike Looijmans
System Expert
TOPIC Embedded Products B.V.
Materiaalweg 4, 5681 RJ Best
The Netherlands
T: +31 (0) 499 33 69 69
E: mike.looijmans@xxxxxxxx
W: www.topic.nl
